Sharpener for sharpening screwdrivers and a method of using same

ABSTRACT

An apparatus for sharpening the head of a screwdriver is disclosed. The apparatus includes a grinder stone having a grinding surface for engaging the one or more front surfaces of the head of the screwdriver for grinding the one or more front surfaces, and a rotor coupling to the grinder. The rotor, in response to a press force applied from the head of the screwdriver to the grinder stone, rotates the grinder stone for grinding the one or more front surfaces of the head of the screwdriver.

FIELD OF THE DISCLOSURE

The present invention relates generally to a sharpener, and in particular to a sharpener for sharpening screwdrivers or screwdriver bits.

BACKGROUND

Screwdrivers have been widely used for driving screws into materials such as wood, plastic, steel, concrete, and the like. Screwdriver bits have also been widely used with power tools for driving screws. It has been observed that screwdrivers or screwdriver bits may wear out after a period of time of use, due to the damage to the heads thereof that engage screws. Worn or damaged screwdrivers or bits are usually thrown away, increasing cost to users and causing burden to the environment.

Screwdriver sharpeners are known. For example, U.S. Pat. No. 4,590,651 to Roberts teaches a handheld sharpener for sharpening worn Phillips-head screwdrivers. The sharpener contains four files that fit into the grooves of a Phillips-head screwdriver. The worn Phillips-head screwdriver is sharpened when the worn Phillips-head screwdriver is moved in-and-out of the sharpener.

While advances have been made in saving worn or damaged screwdrivers, it is always a desire to develop improved methods and apparatus for sharpening screwdrivers or screwdriver bits of various types.

SUMMARY

According to one aspect of this disclosure, there is provided a screwdriver sharpener for sharpening a screwdriver having a fluted shank. The sharpener comprises a housing; a tubular guide for attaching to the housing and guiding and supporting the Phillips screwdriver within the sharpener; an abrader head, rotatably supported within the sharpener for engaging a head of the screwdriver; and a manual, axially-reciprocating drive mechanism for rotating the abrader head when forcibly engaged by the head of the screwdriver, wherein the drive mechanism further comprises a guide secured to the abrader head, a spring disposed about the guide for permitting the abrader head to be reciprocally stroked within the sharpener, and a guide body for causing the guide and abrader head to rotate in a first direction and alternately in a second opposite direction when the abrader head is reciprocally stroked within the sharpener.

According to another aspect of this disclosure, there is provided an apparatus for sharpening a screwdriver or screwdriver bit, said screwdriver or screwdriver bit has a shank defining a longitudinal axis thereof, the shank having a predefined head profile, the head profile comprising one or more front surfaces, each of the one or more front surfaces having a non-zero angle to the longitudinal axis of the shank. The apparatus has a longitudinal axis thereof and comprises: a grinder stone having a grinding surface for engaging and grinding the one or more front surfaces of the screwdriver to restore the predefined head profile; and a rotor coupling to the grinder, said rotor, in response to a press force applied from the head of the screwdriver to the grinder stone, rotating the grinder stone for grinding the one or more front surfaces of the screwdriver.

In one embodiment, the screwdriver comprises a Phillips-type head having a plurality of tapered front surfaces, each front surface at an acute angle to the longitudinal axis of the shank. Accordingly, the grinder stone comprises a conical recess concentric to the longitudinal axis of the apparatus, the surface of the recess at said acute angle to the longitudinal axis of the apparatus, the surface of the recess being the grinding surface.

In one embodiment, the screwdriver comprises a flat head having a front surface orthogonal to the longitudinal axis of the shank. Accordingly, the grinder stone comprises a flat grinding surface orthogonal to the longitudinal axis of the apparatus.

In one embodiment, the screwdriver comprises a square head having a front surface orthogonal to the longitudinal axis of the shank. Accordingly, the grinder stone comprises a flat grinding surface orthogonal to the longitudinal axis of the apparatus.

In one embodiment, the screwdriver comprises a square head. Accordingly, the grinder stone comprises a cylindrical recess, the bottom surface of the recess being the grinding surface and orthogonal to the longitudinal axis of the apparatus.

In one embodiment, in response to the press force applied from the head of the screwdriver, the grinder rotates in a first direction.

In one embodiment, the rotor comprises: at least one pin coupled to the grinder stone; and a guide having at least one helical groove for engaging the at least one pin and guiding the at least one pin to slide therein.

In one embodiment, the apparatus further comprises: a housing for receiving the grinder stone and the rotor and for supporting the grinder stone against the rotor.

In one embodiment, said housing forms a passage concentric to the longitudinal axis of the apparatus for receiving and guiding the head of the screwdriver to the grinder stone of the grinder.

In one embodiment, the rotor further comprises a biasing component sandwiched between the grinder stone and the guide for biasing the grinder stone along a second direction when the press force is reduced.

In one embodiment, the biasing component is a spring.

According to another aspect of this disclosure, there is provided a method of sharpening a screwdriver, said screwdriver having a shank defining a longitudinal axis thereof, the shank having a predefined head profile, the head profile comprising one or more front surfaces, each of the one or more front surfaces having a non-zero angle to the longitudinal axis of the shank. The method comprises: forcibly engaging the one or more front surfaces with a grinding surface to apply a press force from the one or more front surfaces to the grinding surface; and in response to the press force, rotating the grinder surface for grinding the one or more front surfaces of the screwdriver to restore the predefined head profile.

In one embodiment, the screwdriver comprises a Phillips-type head having a plurality of tapered front surfaces, each front surface at an acute angle to the longitudinal axis of the shank. Accordingly, said forcibly engaging the one or more front surfaces with a grinding surface comprises: forcibly engaging the one or more front surfaces with a conical grinding surface of a conical recess of a grinder stone, said conical grinding surface concentric to a longitudinal axis of the grinder stone and at said acute angle thereto.

In one embodiment, the screwdriver comprises a flat head having a front surface orthogonal to the longitudinal axis of the shank. Accordingly, said forcibly engaging the one or more front surfaces with a grinding surface comprises: forcibly engaging the one or more front surfaces with a flat grinding surface of a grinder stone, said flat grinding surface orthogonal to a longitudinal axis of the grinder stone.

In one embodiment, the screwdriver comprises a square head having a front surface orthogonal to the longitudinal axis of the shank. Accordingly, said forcibly engaging the one or more front surfaces with a grinding surface comprises: forcibly engaging the one or more front surfaces with a flat grinding surface of a grinder stone, said flat grinding surface orthogonal to a longitudinal axis of the grinder stone.

In one embodiment, the screwdriver comprises a square head. Accordingly, said forcibly engaging the one or more front surfaces with a grinding surface comprises: forcibly engaging the one or more front surfaces with a grinding bottom surface of a cylindrical recess of a grinder stone, said grinding bottom surface orthogonal to a longitudinal axis of the grinder stone.

In one embodiment, the method further comprises: in response to the press force applied from the one or more front surfaces, rotating the grinding surface in a first direction.

In one embodiment, the method further comprises: coupling at least one pin to the grinding surface; and said in response to the press force, rotating the grinder surface comprises: in response to the press force, guiding the at least one pin through at least one helical groove for rotating the grinder surface.

In one embodiment, the method further comprises: receiving and guiding the one or more front surfaces through a passage for forcibly engaging the one or more front surfaces with the grinding surface.

In one embodiment, the method further comprises: biasing the grinding surface to rotate in a second, reversed direction when the press force is reversed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a shank portion of a conventional Phillips-head screwdriver;

FIG. 2 is an end view of the shank portion of the Phillips-head screwdriver of FIG. 1;

FIG. 3 is a perspective view of a screwdriver sharpener for sharpening a Phillips-head screwdriver, according to one embodiment;

FIG. 4 is a cross-sectional view of the screwdriver sharpener along section A-A of FIG. 3;

FIG. 5 is a perspective view of a grinder stone and a portion of a rotor of the screwdriver sharpener of FIG. 3;

FIG. 6 is a perspective view of a guiding nut of the screwdriver sharpener of FIG. 3;

FIGS. 7A to 7E show an example of sharpening a screwdriver head in various stages of using the screwdriver sharpener of FIG. 3 and shown in cross-section of FIG. 4;

FIG. 8 is a perspective view of a guiding nut of the screwdriver sharpener of FIG. 3, according to an alternative embodiment;

FIG. 9 is a perspective view of a guiding nut of the screwdriver sharpener of FIG. 3, according to another embodiment;

FIG. 10 is a cross-sectional view of a portion of the screwdriver sharpener along section A-A of FIG. 3, according to an alternative embodiment;

FIG. 11 is a cross-sectional view of the screwdriver sharpener along section A-A of FIG. 3, according to an alternative embodiment for sharpening flat-head screwdrivers;

FIG. 12 is a perspective view of a grinder stone and a portion of a rotor of the screwdriver sharpener of FIG. 3, according to the embodiment of FIG. 11;

FIG. 13 is a side view of a portion of a flat-head screwdriver;

FIG. 14 is a front view of the flat-head screwdriver of FIG. 13;

FIG. 15 is a side view of a portion of a square-head screwdriver;

FIG. 16 is a front view of the square-head screwdriver of FIG. 15;

FIG. 17 is a cross-sectional view of the screwdriver sharpener along section A-A of FIG. 3, according to an alternative embodiment;

FIG. 18 is a perspective view of a grinder stone and a portion of a rotor of the screwdriver sharpener of FIG. 3, according to the embodiment of FIG. 17;

FIG. 19 is a cross-sectional view of a screwdriver sharpener for sharpening a Phillips-head screwdriver, according to an alternative embodiment;

FIG. 20 is a side view of a screwdriver sharpener, according to an alternative embodiment;

FIG. 21 is a side view of the screwdriver sharpener of FIG. 20, having a screwdriver inserted therein;

FIG. 22 is a side view of a screwdriver sharpener, according to another embodiment; and

FIG. 23 is a side view of the screwdriver sharpener of FIG. 22, having a screwdriver inserted therein, and snapped to a belt.

DETAILED DESCRIPTION

Herein, a screwdriver sharpener is disclosed. The screwdriver sharpener may be used for sharpening a screwdriver or a screwdriver bit. In this disclosure, the terms “screwdriver” and “screwdriver bit” are interchangeably used for referring to a well-known apparatus for engaging a tool head thereof with a socket head of a suitable screw for driving the screw into a material such as wood, plastic, steel, concrete, and the like. As well known in the art, and will be described below, each screwdriver has a predefined head profile, and screwdrivers are usually categorized in accordance with their head profiles, such as Phillips-head screwdriver, flat-head screwdriver, Robertson-head screwdriver, and the like. In use, a screwdriver head may be worn, causing its head profile to be damaged. Herein, the screwdriver sharpener disclosed herein sharpens a worn screwdriver head to substantially restore its predefined head profile. The term “sharpening” herein refers to the process of restoring damaged screwdriver head to its predefined head profile.

In one embodiment, the screwdriver sharpener disclosed herein is used for sharpening screwdrivers with a Phillips head (Phillips-head screwdriver). FIGS. 1 and 2 respectively show a side view and a front view of a portion of a Phillips-head screwdriver 40. As is well known, the Phillips-head screwdriver 40 comprises a shank 42 having a predefined head profile that is generally made at the time of manufacture. In particular, the shank 42 comprises a front end 48 opposite to a rear end (not shown), the rear end being coupled to a handle or is for coupling to a handling device, e.g., a removable handle or a drill. A head portion 44 of the shank 42, or conventionally, a head 44 of the screwdriver 40, is a portion of the shank 42 adjacent the front end 48, and comprises four blades 46 arranged in a cross configuration such that each adjacent pair of blades 46 are mutually orthogonal. Each blade 46 tapers at the front end 48 of the shank 42 to form a pyramidal, tapered front surface 50. Therefore, herein, a front surface is a surface at the front end 48 of the shank 42 angled to a longitudinal axis S-S of the shank 42. On a Phillips-head screwdriver 40, the head 44 therefore comprises four tapered front surfaces 50 at the front end 48 of the shank 42, with each front surface 50 having an acute angle of a to the longitudinal axis S-S of the shank 42, such that each pair of the opposite front surfaces 50 form a predefined tip angle 2α. In use, the tip end 48 is inserted into corresponding tapered grooves of the socket head of a Phillips-type screw. A torque is then applied to the blades 46 to rotate and drive the screw into a material such as wood. The dimension and angle configuration of the front end 48 and the socket head of the Phillips-type are standardized, and are well known in the art.

When a screwdriver is worn, its predefined head profile is generally worn or damaged. For example, on a worn Phillips-head screwdriver 40, the blades 46 adjacent the tapered front surface 50, and sometimes the tapered front surfaces 50, become damaged such that they are no longer suitable for securely engaging the grooves of the socket head of the Phillips-type screw. Grinding or polishing the tapered front surface 50 to remove the worn portion of the blades 46 would reclaim the blade tip angle 2α, and restore the predefined head profile to recover the screwdriver to a workable condition.

Turning now to FIG. 3, a screwdriver sharpener 100 for sharpening a Phillips-head screwdriver or screwdriver bit is shown. The screwdriver sharpener 100 comprises a hollow, cylindrical housing 102 having a front end 104 and a rear end 106 opposite to the front end. The front end 104 comprises a front opening 108 for receiving a head of a screwdriver. The opening 108 can be conical or beveled for ease of entry of the screwdriver head.

For ease of assembling, the components of the sharpener housing 102 consist of a first portion 102A and a second portion 102B coupled together using securing means such as threads 110. However, those skilled in the art appreciate that other coupling means, such as gluing, nailing, rivet and the like are also readily available in alternative embodiments.

As shown in FIG. 4, the housing 102 may be partitioned, from the front end 104 to the rear end 106, into three (3) sections 112, 114 and 116 having increased inner diameters, respectively, and thus forming a first, rear-facing delimiting shoulder 118 between the first and second sections 112 and 114, and a second, rear-facing delimiting shoulder 120 between the second and the third sections 114 and 116. Section 116 has a rough inner surface.

Section 112 of the housing 102 forms a passage 122 in communication with the front opening 108 for guiding a screwdriver head 44 into the sharpener 100. Adjacent to the passage 122, section 114 of the housing 102 receives therein a grinder stone 124 axially movable between the first and second delimiting shoulders 118 and 120. The opening 108, the passage 122 and the grinder stone 124 are concentric to a longitudinal axis X-X of the sharpener 100, and when a screwdriver 40 is received into the passage 122, the longitudinal axis X-X of the sharpener 100 coincides with the axis S-S of the screwdriver 40.

As shown in FIGS. 4 and 5, the grinder stone 124 is a cylindrical stone made of a suitable abrading material such as aluminum oxide. The grinder stone 124 has an outer diameter larger than the inner diameter of the passage 122 such that, when moving towards the front end 104 of the housing 100, its position is delimited by the first delimiting shoulder 118.

In this embodiment, the grinder stone 124 comprises a conical recess 126 at a front end 128 thereof concentric to the longitudinal axis X-X of the sharpener 100, and in communication with the passage 122. The conical grinding surface 132 of the recess 126 has an apex angle 2β (i.e., the grinding surface 132 having an angle 13 to the axis X-X) equal to the tip angle 2α of the screwdriver tip 48 such that the grinding surface 132 is suitable for engaging the front surfaces 50 of the screwdriver 40 for reclaiming the blade tip angle 2α. In other words, when sharpening a Phillips-head screwdriver, the grinding surface 132 of the recess 126 is in contact with, abrades, and finishes the tapered front surfaces 50 to reclaim the tip angle 2α of the screwdriver tip 48.

With reference to FIGS. 4, 5 and 6, the sharpener 100 also comprises a rotor 140 having a transverse pin 142 with a pair of pin ends 142A and 1426, a spring 144 and a guiding nut 146.

The pin 142 in this embodiment is a cylinder in section 116 arranged orthogonal to the longitudinal axis X-X of the sharpener 100. A shaft 152 is mounted to the center of the pin 142 via suitable means such as welding, gluing or the like, and extends therefrom along the axis X-X to a rear end 130 of the grinder stone 124. The shaft 152 is also mounted to the grinder stone 124 using suitable means, such as welding, gluing or the like, such that the pin 142 and the grinder stone 124 may be rotated together.

Referring to FIGS. 4 and 6, the guiding nut 146 is a hollow cylinder received in section 116. As shown, the guiding nut 146 has a pair of opposite-facing, helical grooves 160 on the inner surface 158 thereof for receiving the pin ends 142A and 142B therein and guiding the pin 142 to rotatably and axially slide therein. The guiding nut 146 also has an outer surface 156 with an outer diameter substantially the same as the inner diameter of the section 116. The second shoulder 120 and the rear wall 106′ of the housing 102 engage the front and rear walls of the guiding nut 146, respectively, preventing the guiding nut 146 from moving axially. The inner surface of the section 116 of the housing 102 and rear wall 106′ frictionally engages the outer surface 156 and rear wall 157 of the guiding nut 146, preventing rotation of the guiding nut 146.

Referring back to FIGS. 4 and 5, the spring 144 is received in section 114 about the shaft 152 and between the grinder stone 124 and the guiding nut 146. The spring 144 normally biases the grinder stone 124 against shoulder 118. The radial distance between the outer and inner walls 156 and 160 of the guiding nut 138 is sufficiently large such that the front wall of the guiding nut 146 has an area sufficient for supporting the spring 144. Similarly, the rear end of the grinder stone 124 also has an area sufficient to support the spring 144.

FIGS. 7A to 7E show an example of using the sharpener 100 to sharpen a screwdriver 40. As shown in FIG. 7A, a user (not shown) inserts the head 44 of the screwdriver 40 into the passage 122 of the sharpener 100 via the front opening 108, and pushes the screwdriver head 44 towards the grinder stone 124, as indicated by the arrow 170. As shown in FIG. 7B, the screwdriver head 44 is pushed into the recess 126 and is in contact with the grinder stone 124 such that the tapered front surfaces 50 engage the conical grinding surface 132 of the recess 126.

As shown in FIG. 7C, further pushing the screwdriver head 44 into the sharpener 100 applies a press force to the grinder stone 124, which in turn applies the press force to the rotor 140. In response to the press force, the rotor 140 rotates the grinder stone 124 to grind the front surfaces 50 of the screwdriver head 44. In particular, the user urges the screwdriver head 44 and the grinder stone 124 to overcome the resistance of the spring 144 and forces the pin 142 to axially slide in the groove 160 towards the rear end 106 of the housing 102. As the groove 160 has a helical shape, the pin 142 also rotates while sliding in the groove 160, causing the grinder stone 124 to rotate in a first direction. As the grinding surface 132 has tightly engaged the tapered front surfaces 50 of the screwdriver head 44 by the user's press force, rotation of the grinder stone 124 grinds the tapered front surfaces 50 of the screwdriver head 44.

As shown in FIG. 7D, when the spring 144 is fully compressed or when the pin 142 has approached the rear wall 106′ of the housing 102, the user reverses the push force to pull the screwdriver head 44 towards the front end 104 of the housing 102, as indicated by the arrow 172. The spring 144 then biases or pushes the grinder stone 124 towards the front end 104 of the housing 102, which pulls the pin 142 to slide in the groove 160 towards the front end 104 of the housing 102, and rotate with a second, reversed rotation direction (See FIG. 7E). As a result, the grinder stone 124 is also rotated, returning the grinder stone 124 to the start position. Some grinding of the tapered front surfaces 50 of the screwdriver head 44 can also occur.

The reciprocating or stroking in-and-out process of FIGS. 7A to 7E may be repeated a plurality of times as the user desires. The worn portion of the blades 46 is removed by grinding and the tapered front surfaces 50 are reclaimed. The screwdriver 40 is then recovered to a workable condition. Material is removed from the screwdriver head 44 in each grinding, the greatest life of a screwdriver is achieved when the shank 42 has an extended longitudinal blade profile of FIG. 1.

Those skilled in the art appreciate that various alternative embodiments are readily available. For example, in an alternative embodiment, the pin 142 only comprises one pin end 142A for coupling to the groove 160. Correspondingly, the guiding nut 146 would only comprise one groove 160 for pin 142 to rotatably slide therein.

In an alternative embodiment, the second portion 102B of the housing 102 may be a cap coupled to the first portion 102A.

As shown in FIG. 8, in an alternative embodiment, the guiding nut 146 may comprise one or more rotational delimiting pins 182 on the rear wall thereof for engaging one or more corresponding delimiting recesses (not shown) on the rear wall 160′ of the housing 102 for preventing the guiding nut 146 from rotating.

As shown in FIG. 9, in another embodiment, the guiding nut 146 may comprise one or more axially arranged grooves 184 on its outer surface for engaging one or more corresponding axially arranged tongues (not shown) on the side wall of the housing 102 for preventing the guiding nut 146 from rotating. Of course, other alternative methods of preventing the guiding nut 146 from rotating are also readily available. For example, the guiding nut 146 may alternatively be screwed to the housing 102 to prevent it from rotating and from axially moving.

In above embodiments, the shoulders 118 and 120 are formed by different diameters of sections 112, 114 and 116. In an alternative embodiment as shown in FIG. 10, the housing 102 has a same inner diameter over its entire length, and the shoulder 118 is formed by inwardly extending tongue 186 along a perimeter of the inner surface of the housing 102. Although not shown, the shoulder 120 is also formed in a similar manner.

In above embodiments, the housing 102 has a cylindrical shape. In another embodiment, the housing 102 may have another suitable shape, such as a cubical shape or the like.

In above embodiments, the sharpener 100 is used for sharpening a Phillips-head screwdriver or screwdriver bit. In some alternative embodiments, the sharpener 100 may comprise a grinder stone 124 with a different grinding surface 132 for grinding screwdrivers or screwdriver bits with other types of blades.

For example, as shown in FIGS. 11 and 12, in an alternative embodiment, the sharpener 100 may comprise a grinder stone 124 having a flat grinding surface 132 orthogonal to the longitudinal axis X-X of the sharpener 100 for sharpening and re-orienting to orthogonal a flat-head screwdriver. In other words, the angle 13 between the grinding surface 132 and the axis X-X is 90°, and the apex angle 2β of the grinding surface is 180°.

As shown in FIGS. 13 and 14, a flat-head screwdriver 180 comprises a shank 182 having a predefined head profile that is generally made at manufacturing. In particular, the shank 182 comprises a front end 184, and a head 186 adjacent the front end 184. The head 186 comprises a pair of tapered side walls 188, tapering to a flat front surface 190 orthogonal to a longitudinal axis S-S of the shank 182. In other words, the angle α between the front surface 190 and the axis S-S is 90°, and the tip angle 2α of the front surface 210 is 180°.

When a flat-head screwdriver 180 is worn, its predefined head profile is generally worn or damaged. For example, the corners between the front surface 190 and the side walls 188 are damaged, and the front surface 190 may be worn, such as rounded, and no longer orthogonal to the axis S-S, such that the front surface 190 is no longer suitable for securely engaging the corresponding groove of the socket head of a flat-type screw.

By inserting the head 186 of the flat-head screwdriver 180 into the sharpener 100 of FIGS. 11 and 12, and repeatedly pushing and pulling the screwdriver 180 in a manner similar to that described above, the flat grinding surface 132 engages the front surface 190 and grinds or polishes the front surface 190 to remove the worn portion of the head 186, restoring the predefined head profile to recover the screwdriver 180 to a workable condition. However, due to the tapered side walls 188, grinding the front surface 190 also enlarges the width and thickness thereof, and extensive sharpening thereof would make the front surface 190 too wide and/or thick to fit into the recess of the socket head of a flat-type screw. Therefore, a flat-head screwdriver 180 may only be sharpened for a limited number of times.

The sharpener 100 in FIGS. 11 and 12 may also be used for sharpening a Robertson or square-head screwdriver. As shown in FIGS. 15 and 16, a square-head screwdriver 200 comprises a shank 202 having a predefined head profile that is generally made at manufacturing. In particular, the shank 202 comprises a front end 204, and a head 206 adjacent the front end 204. The head 206 comprises four side walls 208, extending to the front end 204 and forming a square, flat front surface 210 orthogonal to a longitudinal axis S-S of the shank 202. In other words, the angle a between the front surface 210 and the axis S-S is 90°, and the tip angle 2α of the front surface 210 is 180°.

When a square-head screwdriver 200 is worn, its predefined square head profile is generally worn or damaged. For example, the corners between the front surface 210 and the side walls 208 are damaged, and the front surface 210 may be worn and no longer orthogonal to the axis S-S, such that the front surface 210 is no longer suitable for securely engaging the recess of the socket head of a square-type screw.

By inserting the head 206 of the square-head screwdriver 200 into the sharpener 100 of FIGS. 11 and 12, and repeatedly pushing and pulling the screwdriver 200 in a manner similar to that described above, the flat grinding surface 132 engages the front surface 210 and grinds or polishes the front surface 210 to remove the worn portion of the head 206, restoring the predefined head profile to recover the screwdriver 200 to a workable condition.

As another example, in an alternative embodiment, a sharpener 100 as shown in FIGS. 17 and 18 may comprise a grinder stone 124 having a cylindrical recess 126 concentric to the longitudinal axis X-X of the sharpener 100, with a size suitable for receiving the head 186 of a flat-head screwdriver 180 or the head 206 of a square-head screwdriver 200. The recess 126 comprises a flat bottom surface 132 orthogonal to the axis X-X. In other words, the angle 13 between the bottom surface 132 and the axis X-X is 90°, and the apex angle 2β of the bottom surface is 180°. The flat bottom surface 132 acts as a grinding surface for grinding the front surface 190 of a flat-head screwdriver 180 or the front surface 210 of a square-head screwdriver 200 in a manner similar to that described above.

Although in above embodiments, the rotor 140 comprises a spring 144, in an alternative embodiment, the spring 144 may be replaced with another suitable elastic and compressible component such as a rubber ring.

In an alternative embodiment, the guiding nut 146 may be an integrated part of the housing 102.

FIG. 19 is a cross-sectional view of a screwdriver sharpener 300 for sharpening a Phillips-head screwdriver bit, according to an alternative embodiment. Comparing to the screwdriver sharpener of FIG. 4, the screwdriver sharpener 300 does not comprise any rotator. Rather, it only comprises, in the housing 102, a passage 122 and a grinder stone 124 having a conical recess 126 at a front end 128 thereof concentric to the longitudinal axis X-X, and in communication with the passage 122. The conical grinding surface 132 of the recess 126 has an apex angle 2β, and is used for sharpening the front surfaces of a Phillips-head screwdriver bit. The grinder stone 124 is not rotatable with respect to the housing 102.

In use, a user may clinch a worn Phillips-head screwdriver bit to a power drill, insert the screwdriver bit into the passage 122 via the front opening 108, and pushes the screwdriver head against the grinder stone 124. Then the user turn on the power drill to rotate the screwdriver bit while maintaining the screwdriver bit against the grinder stone 124. The worn front surfaces of the screwdriver bit are then abraded and restored to the predefined head profile for recovering the screwdriver bit to a workable condition.

Alternatively, one may manually hold a worn Phillips-head screwdriver (or screwdriver bit), insert the screwdriver into the passage 122 via the front opening 108, pushes the screwdriver head against the grinder stone 124, and manually rotate the screwdriver to abrade the worn front surfaces of the screwdriver for restoring them to the predefined head profile to recover the screwdriver bit to a workable condition.

Of course, those skilled in the art appreciate that, in some alternative embodiments, the screwdriver sharpener 300 may alternatively have a grinder stone with other suitable grinding surfaces as described above, for sharpening other types of screwdriver bits.

FIGS. 20 and 21 show a screwdriver sharpener 400. In this embodiment, the screwdriver sharpener 400 is generally a screwdriver sharpener 100 of FIGS. 3 and 4 having a clip 402 coupled thereto. In particular, the clip 402 comprises a spring head 404, and is coupled to a front end 104 of the screwdriver sharpener 100 such that the spring head 404 extends beyond the front end 104.

As shown in FIG. 21, many screwdrivers, such as the screwdriver 410 in FIG. 21, have a handle 412 that comprises a circumferential recess 414 adjacent the shank thereof. The spring head 404 has a profile 406 on the side of the screwdriver sharpener 100 substantially suitable for snapping into the circumferential recess 414. As shown in FIG. 21, a user may insert such a screwdriver 410 into the screwdriver sharpener 100 to allow the profile 406 of the spring head 404 of the clip 402 to slide into the circumferential recess 414 of the screwdriver handle 412, and forcibly rest against the screwdriver handle 412. The screwdriver sharpener 400 is then secured with the screwdriver 410 to allow the user to conveniently carry both at the same time.

In yet another embodiment as shown in FIGS. 22 and 23, the spring head 404 of the clip 402 has a profile 406 on the side of the screwdriver sharpener 100 substantially suitable for snapping into the circumferential recess 414, and also has a downwardly facing opening 408 on the side opposite to the screwdriver sharpener 100 for snapping in a tool holder such as a belt.

As shown in FIG. 23, a user may insert a screwdriver 410 into the screwdriver sharpener 100 to allow the profile 406 of the spring head 404 of the clip 402 to slide into the circumferential recess 414 of the screwdriver handle 412, and forcibly rest against the screwdriver handle 412. The screwdriver sharpener 400 is thus secured with the screwdriver 410. Then, the user may then snap the clip 404 to a belt 422 to conveniently carry both the screwdriver sharpener 400 and the screwdriver 410 at the same time.

Although embodiments have been described above with reference to the accompanying drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the scope thereof as defined by the appended claims. 

What is claimed is:
 1. An apparatus for sharpening a screwdriver, said screwdriver having a shank defining a longitudinal axis thereof, the shank having a predefined head profile, the head profile comprising one or more front surfaces, each of the one or more front surfaces having a non-zero angle to the longitudinal axis of the shank, said apparatus having a longitudinal axis thereof and comprising: a grinder stone having a grinding surface for engaging and grinding the one or more front surfaces of the screwdriver to restore the predefined head profile; and a rotor coupling to the grinder, said rotor, in response to a press force applied from the head of the screwdriver to the grinder stone, rotating the grinder stone for grinding the one or more front surfaces of the screwdriver.
 2. The apparatus of claim 1 wherein the screwdriver comprises a Phillips-type head having a plurality of tapered front surfaces, each front surface at an acute angle to the longitudinal axis of the shank; and wherein the grinder stone comprises a conical recess concentric to the longitudinal axis of the apparatus, the surface of the recess at said acute angle to the longitudinal axis of the apparatus, the surface of the recess being the grinding surface.
 3. The apparatus of claim 1 wherein the screwdriver comprises a flat head having a front surface orthogonal to the longitudinal axis of the shank; and wherein the grinder stone comprises a flat grinding surface orthogonal to the longitudinal axis of the apparatus.
 4. The apparatus of claim 1 wherein the screwdriver comprises a square head having a front surface orthogonal to the longitudinal axis of the shank; and wherein the grinder stone comprises a flat grinding surface orthogonal to the longitudinal axis of the apparatus.
 5. The apparatus of claim 1 wherein the screwdriver comprises a square head; and wherein the grinder stone comprises a cylindrical recess, the bottom surface of the recess being the grinding surface and orthogonal to the longitudinal axis of the apparatus.
 6. The apparatus of claim 1 wherein in response to the press force applied from the head of the screwdriver, the grinder rotates in a first direction.
 7. The apparatus of claim 6 wherein the rotor comprises: at least one pin coupled to the grinder stone; and a guide having at least one helical groove for engaging the at least one pin and guiding the at least one pin to slide therein.
 8. The apparatus of claim 1 further comprising: a housing for receiving the grinder stone and the rotor and for supporting the grinder stone against the rotor.
 9. The apparatus of claim 8 wherein said housing forms a passage concentric to the longitudinal axis of the apparatus for receiving and guiding the head of the screwdriver to the grinder stone of the grinder.
 10. The apparatus of claim 1 wherein the rotor further comprises a biasing component sandwiched between the grinder stone and the guide for biasing the grinder stone along a second direction when the press force is reduced.
 11. The apparatus of claim 10 wherein the biasing component is a spring.
 12. A method of sharpening a screwdriver, said screwdriver having a shank defining a longitudinal axis thereof, the shank having a predefined head profile, the head profile comprising one or more front surfaces, each of the one or more front surfaces having a non-zero angle to the longitudinal axis of the shank, said method comprising: forcibly engaging the one or more front surfaces with a grinding surface to apply a press force from the one or more front surfaces to the grinding surface; and in response to the press force, rotating the grinder surface for grinding the one or more front surfaces of the screwdriver to restore the predefined head profile.
 13. The method of claim 12 wherein the screwdriver comprises a Phillips-type head having a plurality of tapered front surfaces, each front surface at an acute angle to the longitudinal axis of the shank; and wherein said forcibly engaging the one or more front surfaces with a grinding surface comprises: forcibly engaging the one or more front surfaces with a conical grinding surface of a conical recess of a grinder stone, said conical grinding surface concentric to a longitudinal axis of the grinder stone and at said acute angle thereto.
 14. The method of claim 12 wherein the screwdriver comprises a flat head having a front surface orthogonal to the longitudinal axis of the shank; and wherein said forcibly engaging the one or more front surfaces with a grinding surface comprises: forcibly engaging the one or more front surfaces with a flat grinding surface of a grinder stone, said flat grinding surface orthogonal to a longitudinal axis of the grinder stone.
 15. The method of claim 12 wherein the screwdriver comprises a square head having a front surface orthogonal to the longitudinal axis of the shank; and wherein said forcibly engaging the one or more front surfaces with a grinding surface comprises: forcibly engaging the one or more front surfaces with a flat grinding surface of a grinder stone, said flat grinding surface orthogonal to a longitudinal axis of the grinder stone.
 16. The method of claim 12 wherein the screwdriver comprises a square head; and wherein said forcibly engaging the one or more front surfaces with a grinding surface comprises: forcibly engaging the one or more front surfaces with a grinding bottom surface of a cylindrical recess of a grinder stone, said grinding bottom surface orthogonal to a longitudinal axis of the grinder stone.
 17. The method of claim 12 further comprising: in response to the press force applied from the one or more front surfaces, rotating the grinding surface in a first direction.
 18. The method of claim 17 further comprising: coupling at least one pin to the grinding surface; and wherein said in response to the press force, rotating the grinder surface comprising: in response to the press force, guiding the at least one pin through at least one helical groove for rotating the grinder surface.
 19. The method of claim 12 further comprising: receiving and guiding the one or more front surfaces through a passage for forcibly engaging the one or more front surfaces with the grinding surface.
 20. The method of claim 12 further comprising: biasing the grinding surface to rotate in a second, reversed direction when the press force is reversed. 